CVE-2025-11847: NULL Pointer Dereference in Zyxel Ax7501-b1 Firmware

15

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 1.8% (30-day exploitation probability)+12
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

1.81%

ahead of 78% of scored CVEs · Oct 14, 2026

Affects

Zyxel

Ax7501-b1 Firmware and 53 more

CVSS base

4.9

Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

No

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Zyxel Ax7501-b1 Firmware, Zyxel Dx3300-t0 Firmware, Zyxel Dx3300-t1 Firmware…).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Zyxel	Ax7501-b1 Firmware	< 5.17\(abpc.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Dx3300-t0 Firmware	< 5.50\(abvy.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Dx3300-t1 Firmware	< 5.50\(abvy.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Dx3301-t0 Firmware	< 5.50\(abvy.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Dx4510-b0 Firmware	< 5.17\(abyl.10.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Dx4510-b1 Firmware	< 5.17\(abyl.10.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Dx5401-b1 Firmware	< 5.17\(abyo.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ee3301-00 Firmware	< 5.63\(acmu.2.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ee5301-00 Firmware	< 5.63\(acld.2.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ee6510-10 Firmware	< 5.19\(acjq.4.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Emg3525-t50b Firmware	< 5.50\(abpm.9.7\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Emg5523-t50b Firmware	< 5.50\(abpm.9.7\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex2210-t0 Firmware	< 5.50\(acdi.2.3\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3300-t0 Firmware	< 5.50\(abvy.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3300-t1 Firmware	< 5.50\(abvy.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3301-t0 Firmware	< 5.50\(abvy.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3500-t0 Firmware	< 5.44\(achr.5.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3501-t0 Firmware	< 5.44\(achr.5.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3510-b0 Firmware	< 5.17\(abup.15.2\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3510-b1 Firmware	< 5.17\(abup.15.2\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex3600-t0 Firmware	< 5.70\(acif.2.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex5401-b1 Firmware	< 5.17\(abyo.7.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex5510-b0 Firmware	< 5.17\(abqx.11.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex5512-t0 Firmware	< 5.70\(aceg.5.3\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex5601-t0 Firmware	< 5.70\(acdz.5.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex5601-t1 Firmware	< 5.70\(acdz.5.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex7501-b0 Firmware	< 5.18\(achn.3.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Ex7710-b0 Firmware	< 5.18\(acak.1.6\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Gm4100-b0 Firmware	< 5.18\(accl.2\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Lte3301-plus Firmware	< 1.00\(abqu.9\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Nebula Fwa505 Firmware	< 1.60\(acko.2\)v0	Vulnerable	NIST National Vulnerability Database
Zyxel	Nebula Fwa510 Firmware	< 1.60\(acgd.0\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Nebula Fwa515 Firmware	< 1.60\(acpz.0\)v0	Vulnerable	NIST National Vulnerability Database
Zyxel	Nebula Fwa710 Firmware	< 1.60\(acgc.1\)v0	Vulnerable	NIST National Vulnerability Database
Zyxel	Nebula Lte3301-plus Firmware	< 1.18\(acca.6\)v0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pe3301-00 Firmware	< 5.63\(acmt.2.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pe5301-01 Firmware	< 5.63\(acoj.2.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pm3100-t0 Firmware	< 5.42\(acbf.4.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pm5100-t0 Firmware	< 5.42\(acbf.4.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pm5100-t1 Firmware	< 5.42\(acbf.4.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pm7300-t0 Firmware	< 5.42\(abyy.4.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Pm7500-00 Firmware	< 5.61\(ackk.1.2\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Px3321-t1 Firmware	< 5.44\(achk.3\)c0< 5.44\(acjb.1.5\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Px5301-t0 Firmware	< 5.44\(ackb.0.6\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Scr 50axe Firmware	< 1.30\(acgn.0\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Vmg3625-t50b Firmware	version <= 5.50(ABPM.9.6)C0	Vulnerable	CVE Program (cve.org) e CISA ADP
Zyxel	Vmg3625-t50b Firmware	< 5.50\(abpm.9.7\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Vmg4005-b50a Firmware	< 5.17\(abqa.3.2\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Vmg4005-b60a Firmware	< 5.17\(abqa.3.2\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Vmg8623-t50b Firmware	< 5.50\(abpm.9.7\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	We3300-00 Firmware	< 5.70\(acka.1.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Wx3100-t0 Firmware	< 5.50\(abvl.4.9\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Wx3100-t0 Firmware	version <= 5.50(ABVL.4.8)C0	Vulnerable	CVE Program (cve.org) e CISA ADP
Zyxel	Wx3401-b1 Firmware	< 5.17\(abve.2.10\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Wx5600-t0 Firmware	< 5.70\(aceb.5.1\)c0	Vulnerable	NIST National Vulnerability Database
Zyxel	Wx5610-b0 Firmware	< 5.18\(acgj.0.5\)c0	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

High

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
4.9	CVSS 3.1	Medium	1.2	3.6	security@zyxel.com.tw via NIST National Vulnerability Database
4.9	CVSS 3.1	Medium	1.2	3.6	nvd@nist.gov via NIST National Vulnerability Database
4.9	CVSS 3.1	Medium	—	—	Zyxel via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-476 · NULL Pointer Dereference

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 1.81%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.

web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

2026
Affected products added · zyxel/vmg3625-t50b firmware, zyxel/wx3100-t0 firmware
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 4.9
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Feb 24, 2026 · Zyxel

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-nul
Vendor Advisory, vendor-advisory, NIST National Vulnerability Database

Elsewhere on this site

Zyxel
every CVE for this vendor

Memory corruption
same class

CWE-476
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-1460 OS Command Injection in Zyxel Nebula Fwa70 Firmware Apr 28, 2026
Medium CVE-2026-0711 OS Command Injection in Zyxel Nr5307 Firmware Apr 28, 2026
Critical CVE-2025-13942 OS Command Injection in Zyxel Wx5610-b0 Firmware Feb 24, 2026
Medium CVE-2025-11848 NULL Pointer Dereference in Zyxel Ex5601-t1 Firmware Feb 24, 2026
High CVE-2025-13943 OS Command Injection in Zyxel Ex5601-t1 Firmware Feb 24, 2026
High CVE-2026-1459 OS Command Injection in Zyxel Vmg3625-t50c Firmware Feb 24, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-11847 is "NULL Pointer Dereference in Zyxel Ax7501-b1 Firmware", rated Medium. It affects Ax7501-b1 Firmware (Zyxel); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.9 describes technical severity. EPSS 1.81% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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